This invention relates generally to the field of therapeutic compositions and more specifically to antisense oligonucleotides that bind to Cyclooxygenase-2 (COX-2) polynucleotides and methods of treatment for diseases associated with COX-2.
Eicosanoids are described as paracrine hormones derived from C20 fatty acids and released from membrane lipids in response to cellular signals. Those compounds are divided into two groups: leukotrienes and prostanoids, both formed from arachidonic acid (AA) by two distinct enzymatic pathways. Prostaglandin synthase (cyclooxygenase, cox) is the main enzyme that catalyzes the first biosynthetic steps of prostanoids conversion from AA. First, the oxidation of AA to prostaglandin G2 and second, the reduction to prostaglandin H2, which is a common precursor for all prostaglandins (PGs), thromboxanes (TBs) and prostacyclines (PIs). The purification of prostaglandin synthase and characterization of its biological activity was first reported in the 1970""s (1), however the first ovine cDNA sequence was cloned a decade later (2). This information was used to clone the human gene (3), which is 25 kilobases (kb) long and contains eleven exons separated by ten introns and produces 2.8 kb long mRNA (4). Until the beginning of this decade it was believed that only one cox gene existed. For many years it was assumed that prostaglandin generation in response to cellular stimulation was limited by AA availability or due to the constitutively expressed enzyme (cox-1) (5). However, the studies of glucocorticoid inhibition of cox activity, prostanoid synthesis and mitogen-induced prostaglandins production suggested the existence of another enzyme (6). The discovery of the second cox gene (cox-2) occurred after the examination of gene expression in chicken embryo cells transformed with RNA tumor viruses (7). The human gene was subsequently cloned (8) showing a substantially smaller gene size of approximately 8 kb (9), but similar to cox-1 exon-intron structure (10). The comparison of cox-1 and cox-2 protein structures reveals 64% overall amino acid identity between enzymes. However, the cox-1 protein contain a short sequence (17 amino acids) at amino terminus that is not present in the cox-2 protein (11) and cox-2 contains another sequence (18 amino acids) at carboxyl terminus that is not present in the cox-1 protein. In spite of structural similarities, there are differences between both enzymes in substrate and inhibitor selectivity, e.g., cox-2 accepts a wider range of fatty acids as substrates than cox-1 (4). Moreover, cox-2 is present on the nuclear membrane and the endoplasmic reticulum (ER), while cox-1 is found only on the ER membranes (12). Cox-1 protein and mRNA was detected in virtually all mammalian tissues (5) and cox-2 mRNA was detected in all examined tissues (14). The constitutive form of the enzyme is now termed cox-1 and the inducible form is called cox-2. The induction of cox-2 gene occurs in response to growth factors, oncogene expression, depolarization in neurons, in hormonal response in osteoblasts, mesangial and granulosa cells, and in inflammatory response in macrophages, neutrophils, epithelial and endothelial cells, synoviocytes, chondrocytes, mast and amnion cells (13, 18). However, cox-2 is constitutively expressed in neurons and gastric mucosa (14, 22). The cox-1 and cox-2 enzymes are respectively called physiological and pathological because most of the stimulatory processes that induce cox-2, are associated with inflammation like bacterial lipopolysaccharide, interleukin-1 and tumor necrosis factor alpha, while cox-1 expression is important in cytoprotection and maintaining physiological functions. The corticosteroids and anti-inflammatory interleukins decrease cox-2 activity (13,15). Most conventional nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cox activity by acetylation of Ser-530 located near the active site, preventing the entrance of substrate AA and its contact with the Tyr-385 active site (20, 21). Moreover, NSAIDs side-effects like gastrointestinal bleeding and renal dysfunction are considered to be caused by the inhibition of cox-1 physiological functions (23). The gene knockout experiments in mice show that cox-1 gene disruption caused platelets unresponsiveness to AA, no gastric or intestinal bleeding nor any renal pathology but reduction of fetus survival (28). The cox-2 knockout strain shows unchanged response to inflammation, but on the other hand infertility due to the lack of ovulation and massive renal developmental deficiencies (29, 30). Prostanoids play important role in human physiology, which is demonstrated by biological and pharmaceutical significance of cox inhibitors. They mediate a variety of intra- and extracellular interactions including homeostasis, bone development, glomerular filtration and water balance, bronchodilatory respiratory function, cryoprotective gastric function, ovulation, fertilization, embryo implantation and development, labor initiation, modulation of immunological responses, sleep and other processes in central nervous system. Prostaglandins show both vasodilatory and venule vasoconstrictory activities.
Cox-1 is the only form detectable in platelets responsible for AA-induced platelets aggregation. Inhibition of cox-1 leads to decreased production of thromboxane A2 in platelets and prostacyclin in endothelial cells. However, cox-1 activity regenerates in endothelial cells and prostacyclin production is reestablished. This effect provides grounds for prophylaxis against thromboembolic disease (16). The cytoprotective role of prostanoids in the stomach and intestine is mostly due to their vasodilating abilities causing increased mucosal blood flow and preserving the integrity of mucosal epithelium (19).
High level of Cox-2 is associated with active gastritis caused by bacterium Helicobacter pylori (39). It seem that cox-1 is predominant generator of protective gastric mucosal prostaglandins even with Helicobacter pylori infection raising the possibility of therapeutic selective cox-2 inhibition.
Epidemiological studies showed that chronic intake of NSAIDs decreases the incidence of colon and breast cancers and a 50% reduction in mortality in patients with colorectal cancer (41,42). Similar effect during treatment was observed in young patients with familiar adenomatous polyposis, a pathological condition in which colorectal polyps develop spontaneously and progress to tumors (43). Human breast tumors and colorectal adenomas and adenocarcinomas express higher levels of cox-2 gene and protein than surrounding normal tissues (44,45), providing an attractive therapeutic target.
Similar epidemiological studies showed the correlation between cox enzymes, prostaglandin production and Alzheimer""s disease (AD), Parkinson""s disease and other neurogenerative diseases. AD is a progressive dementing illness characterized by pathological features like neuritic amyloid plaques, neurofibrillary tangles, loss of neuronal cells and synapses and increased gliosis. Several studies disclosed 50% reduced risk for AD in individuals taking NSAIDs (46,47) and reduced severity and incidence of AD (48). Inflammatory events like increased expression of proinflammatory cytokines such as interleukin-1 and tumor necrosis factor alpha, intracellular adhesion molecule ICAM-1, complement cascade and acute phase protein alpha-1 antichymotrypsin all are present in AD (49, 50, 51, 52). Cox-2 but not cox-1 mRNA expression is elevated in cerebral cortex and hippocampal formation of AD brain and cox-2 protein content correlates with the amount of amyloid plaques (53). A major therapeutic benefit of the new selective cox-2 inhibitors can lead to delaying or preventing AD in subject genetically at risk. Inflammation contributes also to ischemic stroke and cox-2 increased expression is present after stroke in damage neurons causing accelerated apoptotic death. The reduced expression of cox-2 by drugs inhibiting microglial activation after stroke is associated with increased neuronal survival (54).
Recent finding suggest that cox-2 is a major source of systemic prostacyclin synthesis in healthy subjects (61). The increased production of prostacyclin is observed in patients with signs of platelets activation such as unstable angina, severe atherosclerosis and during angioplasty (62, 63, 64).
This invention relates to antisense oligonucleotides that bind to polynucleotides encoding COX-2, thus preventing production of a COX-2 polypeptide. The present invention provides antisense oligonucleotides that inhibit COX-2 expression, and use thereof to reduce activity of COX-2 in tissues, in order to treat diseases such as rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, chronic liver disease, ulcerative colitis, cell proliferative disorders and inflammation associated with Alzheimer""s Disease and stroke. The invention features use of antisense oligonucleotides to treat such diseases by inhibiting the synthesis of COX-2 and preventing the recruitment and activation of macrophages.
The invention features antisense oligonucleotide molecules that specifically bind polynucleotides encoding COX-2. In a preferred embodiment the antisense oligonucleotides bind mRNA or precursor mRNA encoding COX-2. In another embodiment, the antisense oligonucleotides are about 8 to about 30 nucleic acids in length and can be either DNA or RNA. However, other lengths including, for example, about 8 to 11 and about 21 to 30 nucleotides are also contemplated by the present invention. The antisense oligonucleotides may be chemically modified. In another embodiment, they oligonucleotides of the present invention have mixed backbones (e.g., partially phosphodiester and partially phophorothioate) or chimeric structures (e.g., sugar modified bases and backbone modifications).
In another embodiment, the invention features a method for suppressing COX-2 production in a cell by administering to the cell an amount of antisense oligonucleotide molecules sufficient to specifically bind polynucleotides encoding COX-2, thereby suppressing COX-2 levels. In another aspect, the invention features a method for treating a subject having or at risk of having an COX-2-associated disorder, by administering to the subject an effective amount of antisense oligonucleotide which specifically binds mRNA or precursor-mRNA encoding COX-2. The COX-2 disorder may be an inflammatory disorder, for example. In a particular embodiment, the disorder is rheumatoid arthritis.
In still another aspect, the invention provides a pharmaceutical composition for treatment of a disorder associated with COX-2. The composition comprises an antisense oligonucleotides of the invention either alone, or in combination with other antisense molecules or pharmaceutical agents.
The invention provides several advantages. For example, the antisense oligonucleotides of the invention are specific for COX-2 polynucleotides. A further advantage of the present invention is that the antisense oligonucleotide molecules can be delivered exogenously or can be expressed from DNA or RNA vectors that are delivered to specific cells. In a preferred embodiment the antisense oligonucleotides are provided by transcription of a recombinant DNA sequence. The recombinant DNA sequence may be in a plasmid or viral vector.
In yet another embodiment, a method of monitoring the effectiveness of suppressing COX-2 expression after administering a therapeutically effective amount of the antisense oligonucleotide is provided, the method comprises detecting COX-2 levels before and after the antisense therapy.